This invention relates in general to fixtures for mounting vehicle wheel castings on machine tools during finishing operations and in particular to pylons for fixtures for mounting wheel castings having wheel discs of differing recess depths upon a wheel lathe for machining.
Lightweight alloy vehicle wheels are becoming increasingly popular. Such wheels typically include an annular wheel rim that carries a tire. The wheel rim has a recessed center portion that facilitates mounting the tire upon the rim. The ends of the wheel rim include inboard and outboard tire bead seats that support the tire. Inboard and outboard tire bead retaining flanges are formed on the ends of the wheel rim to retain the tire upon the wheel rim.
A circular wheel disc is formed across one end of the wheel rim. The wheel disc usually includes a central hub portion supported within the wheel rim by a plurality of wheel spokes. A central pilot hole and plurality of wheel mounting holes are formed through the wheel hub. The mounting holes are drilled equally spaced about a circle that is concentric with the pilot hole. The central pilot hole is used to position the wheel on a vehicle and the mounting holes are used to secure the wheel to the vehicle.
One conventional process for manufacturing lightweight alloy wheels involves pouring molten metal into a wheel mold to form a casting of the wheel. After the molten metal solidifies, the wheel casting is removed from the mold. The wheel casting is oversized and is machined to final shape with machining operations.
Finishing the wheel casting typically includes multiple machining operations. Sawing machines cut any casting gates and risers from the wheel casting. A drilling machine is used to drill the central pilot hole and the wheel mounting holes through the wheel hub. The wheel casting is mounted upon a lathe for machining to its final shape. During the lathe operations, the inside surface of the wheel hub is usually faced to provide a flat mounting surface. Similarly, the outboard wheel hub surface is faced and both the inside and outside of the wheel rim are turned to their final shapes. During the finishing of the outside of the wheel rim, the tire bead seats are turned to their final diameter. Additionally, portions of the wheel can be painted or covered with a clear coating to protect the wheel from corrosion and/or enhance its appearance.
The machining operations are carried out with highly automated machining stations, which usually include numerically controlled machine tools designed to complete one or more specific machining operations. The wheels are sequentially moved between the machining stations, with the machine tool located at each station completing a portion of the required machining. For example, a typical wheel production facility can include multiple lathe stations. The production facility can include a first lathe station for facing the inboard wheel hub surface, a second lathe station for facing the outboard wheel disc surface, a third lathe station to turn the inside surface of the wheel rim and a fourth lathe station to turn the outside surface of the wheel rim. Alternately, the production facility can include a lathe capable of multiple machining operations to perform several of the above operations at a single machining station. Mounting fixtures are typically designed for each machine tool to facilitate mounting and dismounting the wheels on the tool.
Referring now to the drawings, there is shown in FIG. 1 a sectional view of a known fixture, generally indicated at 10, for mounting a vehicle wheel upon a lathe in accordance with the prior art. In the interest of simplicity, fasteners, which secure components of the mounting fixture 10 to one another, are not shown in FIG. 1. A typical vehicle wheel 15, which will be described below, is shown mounted on the fixture 10.
The mounting fixture 10 includes an adapter plate 20 that can be secured to the rotatable spindle of a lathe (not shown) by conventional means. The adapter plate 20 includes a circular base 21 that has a central circular opening 22 formed therethrough. The adapter plate 20 also includes a cylindrical sleeve 23 extending axially from the base 21. The sleeve 23 has a plurality of axial slots 24 (one shown) formed there through that are spaced equally about the circumference of the sleeve 24. The purpose of the slots 24 will be explained below. The adapter plate 20 further carries a plurality of guide pins 25 (one shown) which extend axially from the base 21.
The mounting fixture 10 also includes a circular face plate 30 that is secured to the end of the adapter plate sleeve 23. The face plate 30 has a central circular opening 31 formed therethrough. A plurality of radial slots 32 (one shown) are formed in the outer edge of the face plate 30. The slots 32 are spaced equally about the circumference of the face plate 30. Each slot 32 has a cam pin 33 mounted transversely thereacross. The purpose for the slots 32 and the cam pins 33 will be explained below. A plurality of part rests 34 (one shown) are mounted upon the outer surface of the face plate 30. The part rests 34 are spaced equally about the circumference of the face plate 30.
The face plate opening 31 receives a generally cylindrical center sleeve 35. The center sleeve 35 has a central axial bore 36 formed therethrough. A pilot tube 40 that corresponds to a particular wheel design is disposed within the center sleeve bore 36. The pilot tube 40 has a piston bore 41 formed therethrough. A counter bore 42 is formed in the end of the piston bore 41 facing the wheel 15. A flange 43 is formed on the outer end of the pilot tube 40. A first plurality of compression springs 44 (one shown) are disposed between the pilot tube flange 43 and the end of the center sleeve 35 facing the wheel 15.
The pilot tube flange 43 also carries a plurality of locator pins, or pylons, 45 (one shown). As best seen in FIG. 2, each locator pylon 45 includes a mounting shaft 84 extending generally perpendicularly from the pilot tube flange 43. The mounting shaft 84 has a first end 85 and a second end 86. The first end 84 is slidingly received in a corresponding aperture 18 formed in the pilot tube flange 43. A plurality of threads 87 are formed upon the second end 86 of the mounting shaft 84. The locator pylon 45 includes a support shaft 88. The support shaft 88 has a first end 89 adjacent to the mounting shaft 84 and a second end 90. The support shaft 88 has a threaded bore 91 extending longitudinally into the first end 89. The threaded bore 91 cooperates with the support shaft threads 87 to secure the support shaft 88 to the mounting shaft 84. The support shaft 88 cooperates with the mounting shaft 84 to define a fixed axial length for the locator pylon 45. The fixed axial length of the locator pylon 45 is selected to correspond to a specific wheel, such as the wheel 15, as will be discussed below. The support shaft 88 has an annular retaining flange 92 formed about the second end 90. The locator pylon 45 includes a generally cylindrical stop 93 formed from a resilient material. The stop 93 is typically made of an elastomer as to cushion the mounting of the wheel 15 upon the fixture 10. The stop 93 has a first end 94 adjacent to the support shaft retaining flange 92 and a second end 95. The stop 93 also has an annular recess 96 extending into the first end 94. The stop 93 includes an annular lip flange 97, at least partially defining the recess 96. The annular lip flange 97 cooperates with the annular retaining flange 92 to secure the stop 93 to the support shaft 88. The stop 93 is sized to fit the wheel mounting holes 80 of the wheel 15.
Referring again to FIG. 1, the mounting fixture 10 also includes a piston 50 that is disposed within the pilot tube bore 41. The piston 50 has an end 51 facing the wheel 15 that is formed to contact the center portion of a wheel hub. The piston end 51 has a greater diameter than the remainder of the piston 50 and defines a shoulder 52 therebetween. A second plurality of compression springs 53 (one shown) are disposed between the piston shoulder 52 and the pilot tube flange 43.
The mounting fixture 10 further includes an axially movable yoke plate 60 that is disposed within the adapter plate sleeve 23. The yoke plate 60 is circular and has a plurality of guide pin holes 61 formed therethrough. Each of the guide pin holes 61 slidably receives one of the guide pins 25. The yoke plate 60 also has a plurality of radially extending arms 62 (one shown) that are spaced equally about the circumference of the yoke plate 60 and which extend through the adapter plate slots 24. An actuator bar 63 is secured to the center of the yoke plate 60 and extends axially through the adapter plate opening 22. The actuator bar 63 is connected to a conventional means for axially shifting the actuator bar and yoke plate assembly.
A plurality of cam arms 65 (one shown) are pivotally mounted on the ends of the yoke plate arms 62. A first end of each cam arm 65 is secured to each yoke plate arm 62 with a pivot pin 66. The center portion of each cam arm 65 has a generally L-shaped cam slot 67 formed therethrough. The cam slots 67 have a generally axial first portion 67A and a second portion 67B that is directed in a radially inward direction. Each cam slot 67 receives a corresponding cam pin 33. A removable cam arm jaw 68, which is shaped to clamp over a portion of a vehicle wheel rim, is attached to a second end of each cam arm 65.
As indicated above, the mounting fixture 10 is operative for clamping a vehicle wheel 15 to a lathe for machining the wheel 15 to its final shape. As shown in FIG. 1, the vehicle wheel 15 includes an annular wheel rim 70 having a circular wheel disc 71 formed across one end thereof. The wheel rim 70 includes a central drop well 72 and inboard and outboard tire bead seats 73 and 74. The outer ends of the wheel rim 70 are formed into inboard and outboard tire retaining flanges 75 and 76, respectively. The wheel disc 71 includes a central hub 77 supported within the wheel rim 70 by a plurality of wheel spokes 78 (one shown). The hub has a central pilot hole 79 and a plurality of wheel mounting holes 80 (one shown) formed therethrough.
The operation of the prior art mounting fixture 10 will now be described. The actuator bar 63 is axially extended into the adapter plate sleeve 23, axially shifting the yoke plate 60 away from the adapter plate base 21. As the yoke plate 60 is axially displaced, the cam slot 67 in each cam arm 65 slides along the corresponding cam pin 33. The cam pins 33 cooperate with the cam slots 67 to urge the cam arms 65 in an outward radial direction, thereby opening the mounting fixture 10. With the mounting fixture 10 opened, the wheel 15 can be mounted upon the mounting fixture 10. The wheel hub 77 is placed adjacent to the outer end 51 of the piston 50 with the outboard tire bead retaining flange 76 engaging the part rests 34. The locator pylons 45 are received by corresponding wheel mounting holes 80. The actuator bar 63 is then retracted, moving the yoke plate 60 axially towards the adapter plate base 21. As the yoke plate 60 is moved towards the yoke plate base 21, the cam slots 67 in each of the cam arms 65 is drawn back over the cam pins 33. The cam pins 33 cooperate with the cam slots 67 to urge the cam arms 65 in an inward radial direction, thereby causing the jaws 68 to move to a closed position and clamp onto the wheel flange 76. As the cam arms 65 continue to be drawn back, the wheel flange 76 is drawn firmly against the part rests 34. Additionally, the piston end 51 facing the wheel 15 is axially shifted by the wheel hub 77, compressing the first and second sets of compression springs 44 and 53. When the lathe is started, the locator pylons 45 cooperate with the wheel mounting holes 80 to rotate the wheel 15.
While the wheel 15 is shown having a wheel disc 71 located near an end of the wheel rim 70, it will be appreciated that the wheel disc 71 also can be recessed within the wheel rim 70 at a greater or lesser depth. For such wheels, a different pilot tube and piston having a greater or lesser axial length would be substituted for the ones shown in FIG. 1.
As shown in FIG. 1, the locator pylons 45 are positioned to cooperate with the wheel mounting holes 80. As described above, the locator pylons 45 are rigidly mounted upon the pilot tube flange 43 with a fixed axial length. The overall length of the locator pylons 45 is selected as a function of the specific recess depth of the wheel disc 71 within the wheel 15. In order to mount a wheel having a wheel disc with a different recess depth, regardless of the wheel diameter, it is necessary either to replace the entire pilot tube and piston assembly with an assembly that will correspond to the wheel having a wheel disc of differing recess or at least to replace the locator pylons 45 with locator pylons that will cooperate with the wheel having a wheel disc of differing recess. Alternately, a second lathe can be used to machine the wheel of different diameter or the wheel having a wheel disc of differing recess. The procedure to reconfigure the wheel fixture 10 is time consuming and the use of a multiple lathes is costly. Accordingly, it would be desirable to provide a wheel fixture suitable for wheels having wheel discs with different recess depths.